The present invention relates, in general, to devices in electronic circuits having a low power, sleep mode of operation and, more particularly, to wake-up circuits for use with such controls.
In many electronic control applications, an electronic or computer processor based controller has a low current, stand-by mode, also known as a “sleep mode”, in which almost no functionality is provided. A wake-up signal is generated to bring the controller out of the sleep mode and into a normal, fully functional mode. To cause this mode change, a digital signal is needed in the form of an active high or low level signal. The trigger for this signal could be, for example, a change of a switch position. For example, in a controller for a motor vehicle, digital signals can be generated simply and inexpensively from an on/off switch change, such as the activation of a horn switch, movement of a turn signal switch, etc.
However, other switches in a vehicle generate analog outputs, such as resistor multiplexed outputs for controlling headlights, interior instrumental panel and interior dome lights, etc. A contactor moveable over switch pad in response to user caused movement of an actuator couples different resistors in series to generate different voltage output signals depending upon the switch position. The voltage output is read by the controller which implements the function specified by the switch based on the detected voltage level.
Since it is desirable to generate a digital wake-up signal from such analog switches, a common solution is to provide an additional conductor, contact bridge and other mechanical components in parallel to the analog switch signal circuit. However, this requires additional components as well as more area on the circuit board where space is usually at a premium.
Thus, it would be desirable to provide a digital wake-up signal from an analog switch signal which can be implemented in an existing circuit in an expedient manner with a minimum number of additional components.